The voice was not a shout. It was cold, clear, and cut through the thick, coppery air of the small house with the precision of a scalpel.
"What... is this?"
Utsuro didn't even look up from his "work" at the table. He was humming, using a pair of chopsticks to arrange the noodles in the... bowl. "You're late," he chirped. "And you didn't knock. Rude."
A man stood in the doorway, an immaculate Western suit and hat seeming to repel the grime of the room. Muzan Kibutsuji's plum-red, slitted eyes swept the scene. They didn't register horror. They registered the disgust of a perfectionist finding a flaw in his own garden.
"You," Muzan said, his voice quiet but shaking with a terrible, restrained fury. "You've... made a mess."
"I've made art," Utsuro corrected, still not looking at him. He patted the seat next to him. "Sit down, critic. The soup is still warm."
This... thing... was giving him an order. Muzan's curiosity, for a split second, outweighed his rage. This was an anomaly. An insect that didn't know its place. He would allow it to speak, to understand what it was, before he erased it.
Muzan glided to the table, his movements silent. He did not sit. He looked down at the "art." The heads served as bowls.
"This is pathetic," Muzan hissed. "A child's tantrum. This isn't art. It's... wastage."
"Hmph." Utsuro finally looked up, his red eyes bright and empty. "No taste." He gestured with his chopsticks to the plate in front of Muzan's empty seat.
It was a small, seared piece of... something.
"You haven't even tried the main course," Utsuro said, his grin returning, all charm and teeth. "Go on. It's a... special recipe. The soup has these lovely purple flowers I found... they give the broth such a cool color."
Muzan's intelligent mind, in its arrogance, saw the play. The crude Wisteria broth. A child's poison trap. How... quaint. He was an insect, but a clever insect.
Muzan, the perfect being, decided to humor him. To show this freak what true power was. He would consume the poison and show him how little it mattered. He picked up the piece of meat.
"And this?" Muzan asked, his voice a mocking purr.
"Oh, just a little toy I'm... discarding," Utsuro said. "Go on. Dip it in the flower soup. It's delicious!"
Muzan, with a roll of his eyes, did just that. He placed the seared, purple-flecked meat in his mouth.
He chewed.
And then he froze.
It wasn't just the Wisteria. The Wisteria was a gnat bite, annoying but manageable. It was the meat. It was... potent. It was like him.
But... wrong.
A new, impossible sensation bloomed in his gut. Not just poison, but a profound, biological corruption. His perfect body was... confused.
"What... is this...?" Muzan snarled, a genuine, cold spike of alarm hitting him.
Utsuro beamed, as if he'd just been asked to share a secret.
"It's me!" he said, giggling. "Well, my old genital! It was getting... used. Worn out. I got bored with it, so I grew a new one." He gestured vaguely to himself. "This... is just the leftover toy! I thought, 'Waste not, want not!' And you're the first person I've ever met who's strong enough to taste it! Isn't that... wonderful?"
Muzan's mind... broke.
It wasn't just poison. It was a joke. A joke made of Wisteria and... regenerated... filth. He had been tricked... into eating...
"You... FILTHY... ANIMAL!"
Muzan's rage was absolute. This was not a creature. This was an abomination. An insult to existence itself. He would not just kill it. He would cleanse the world of it.
His arm blurred, a black whip of rage, not at Utsuro, but at his "art."
"NO!" Kie screamed, a final, guttural sound as she lunged from the corner.
Muzan backhanded her without looking. The sound of her neck snapping was like a dry branch. Her body crumpled to the floor.
"You... broke her!" Utsuro shrieked, his face a mask of artistic fury. "I wasn't finished! She was the finale!"
"Your 'performance' is over," Muzan snarled, his body already fighting the alien poison, his rage overriding it. He lunged for the last "toy." He seized Nezuko, his hand clamping over her face. "This one... this one will be my masterpiece!"
He dug his nails into her shoulder, forcing his own demonic blood into the girl's system. Nezuko's body convulsed, her veins turning black.
Triumphant, Muzan stood, his chest heaving. He had won. He had destroyed the "art" and created a new, loyal piece. He had cleansed the room. Now, for the freak.
"You are an insult to life!" Muzan roared, and this time, he didn't hold back.
The small house exploded as Muzan unleashed a fraction of his true power. He didn't just attack; he annihilated. Black, bone-tipped whips erupted from his back, turning the room, the furniture, and Utsuro's body into a vortex of splinters and red mist. He ripped and tore, screaming in pure, cathartic rage, until nothing was left but a crater of gore and wooden shards.
Muzan panted, the alien poison in his gut finally receding, his perfect form slick with his enemy's blood. He had cleansed the stain. He had—
"Giggle."
The sound was impossible. It came from... everywhere.
"Oh, wow," a voice said, dripping with impressed amusement. "That... tickled."
Muzan froze. The red mist... the splinters... stopped moving. They hung in the air, and then, as if pulled by an invisible string, they began to reverse. The gore coalesced, the wood shards flew back, and Utsuro reformed, standing exactly where he was, his clothes immaculate, his smile wider than ever.
"That's a fantastic trick!" Utsuro clapped. "You're so loud! But... you're still not listening. You're a bad audience."
Utsuro raised his hand.
Clutched in his blood-soaked fingers was another heart. Paler, more complex, and beating with an inhuman, panicked speed.
A heart with five chambers.
"I took this... before the tickle-party started," Utsuro said, his grin turning predatory. "While you were... ranting. You're very loud."
Muzan's hand flew to his own chest. He felt... nothing. No pain. No wound. But... he knew.
"But... how...?" Muzan whispered, the poison, the rage, and now this impossible reality crashing down on him.
"You let me eat that," he breathed, his mind finally connecting the dots. "You let me kill her. You... swapped..."
"It was a performance!" Utsuro beamed. "And you were the star! You played the part of 'The Raging God' perfectly! But now... the show is over."
Muzan Kibutsuji, for the first time in a millennium, felt true, absolute, mind-shattering terror.
"Give that back," he commanded, his voice weak.
"Hmm. No." Utsuro looked at the heart, studying it with the detached curiosity of an artist. "It's a wonderful toy. Such a strong, angry little thing. But... It's designed all wrong. So... boring. Let's make it... better."
Before Muzan could even react, a sliver of Utsuro's own finger—a tiny, black, void-like shard—chipped off and dropped onto the beating heart. It didn't just land; it burrowed inside, like a virus, turning the heart's pale flesh a sickening, bruised purple.
"No... NO! WHAT ARE YOU DOING?!" Muzan shrieked.
"An upgrade," Utsuro said simply.
He didn't crush the heart. He didn't throw it away.
He opened his hand.
And the infected heart vanished... only to reappear, with a wet, sickening thud, back inside Muzan's chest.
Muzan screamed.
It was not a scream of pain. It was a scream of violation. He collapsed, clutching his chest, feeling his own, perfect, immortal heart re-integrate... but it was wrong. It was tainted. He could feel... something else... inside it. A cold, empty, laughing presence.
"There," Utsuro said, dusting off his hands. "A little piece of me, for you. My... critic's award."
Utsuro walked to the door, stepping over Kie's body. He paused and looked back at Muzan, who was on his knees, clawing at his own chest, his mind broken.
"Now... you're my performance," Utsuro said, his voice dropping to a cheerful whisper. "Go on. Make some art for me. And please... don't be... boring."
He turned and vanished into the storm, his cheerful humming swallowed by the wind.
Muzan was left alone in the ruined house, with the grotesque tableau of his rival's "art," the sound of his new, failed creation—Nezuko Kamado—howling, and the all-consuming, terrifying realization that he was no longer his own master. He was... a canvas.
...
The storm raged for two days. For two days, Tanjiro Kamado sold charcoal, his mind filled with thoughts of a warm meal and his family's smiles.
When he returned, the first thing that hit him, even from a hundred yards away, was the silence.
The second was the scent.
Blood. So much blood. But underneath it... two new, terrifying smells. One was ancient, cold, and inhuman, a scent of pure, aristocratic power (Muzan). The other... the other was the one that made his stomach clench and his mind recoil. It was a scent of glee. A cloying, sweet, rotten-fruit smell of pure, unadulterated amusement.
He found what was left. He found the "art."
He saw his brothers, seated at the table, their heads served in bowls of noodle soup. He saw Hanako, naked, mutilated, "frozen" by the door. He saw Rokuta, "garnished" in his basket.
And he saw his mother, Kie, near the bedroom, her neck broken by a simple, brutal force. It was different from the others. Violent, but not artistic.
Two monsters. One had "played." The other had... cleaned up.
Then, a howl. Nezuko. She was alive... but she was wrong. The scene that followed was a blur of terror, snow, and blood. His newly turned sister, the lunge, the desperate flight down the mountain.
The scent of a new demon drew a Slayer. A man with a half-and-half haori, his eyes as cold as the ice. Giyu Tomioka.
The fight was desperate. The plea. The hatchet throw. The moment of hesitation as Nezuko, his sister, stood to protect him.
"Go to Urokodaki Sakonji," the Slayer commanded, sparing them. "And keep your sister out of the sun."
Burying them was the hardest part. He had to... undo... the "art." He had to take his brothers' heads from the soup, his hands shaking so violently he could barely hold them. He had to unpose Hanako.
He wept until he had no moisture left. And then, he made his vow.
He would find a cure for Nezuko. And he would find the two monsters responsible. The one who turned her... and the one who laughed.
(A Time Skip)
The two years that followed were a descent into hell. Urokoaki's training pushed Tanjiro to the brink. The air was thin. The traps were lethal.
But his hatred was pure. When he was too tired to move, he wouldn't just remember his family's faces. He would remember the scent of joy that had filled his home. He would remember the art. And a new, cold fury would get him to his feet.
He met Sabito and Makomo. He split the boulder.
He survived Final Selection. He returned, his sword in hand.
While Tanjiro trained, the world turned.
In a fortress of impossible angles, Muzan Kibutsuji writhed. The "upgrade" Utsuro had given him was... torment. It wasn't killing him. It was mocking him. Sometimes, his own flesh would move against his will, a patch of skin briefly erupting into a grotesque, smiling face before he wrestled it back under control. His "perfection" was violated. His search for the Blue Spider Lily was now joined by a new, frantic obsession: find, understand, and destroy the laughing void.
In the Demon Slayer Corps, Giyu's report was met with confusion. A demon protecting a human... and a massacre scene that sounded less like a feeding and more like a performance. An unknown, powerful third player was on the board.
For Utsuro, those two years were a bore. He had wandered, "played" with a few minor demons (messy, boring), and "charmed" some humans (predictable, boring). Nothing... nothing... had matched the sheer, exquisite fun of his performance with the Kamado family and his "critic," Muzan.
He was bored. He needed a new toy.
(Present Day)
"CAW! CAW! MISSION! HEAD TO A MANSION IN THE SOUTH! A DEMON IS USING... DRUMS... TO... PLAY... WITH ITS VICTIMS! CAW!"
Tanjiro gripped his new Nichirin blade. He and his new... acquaintances... Zenitsu and Inosuke were on their way.
A demon who "played" with its victims.
Tanjiro sniffed the air. Under the scent of Zenitsu's terror and Inosuke's rage, he caught something on the wind.
It wasn't just a demon.
He knew that smell. Faint... so faint... but unmistakable.
The scent of joyful, rotten fruit.
"He's here," Tanjiro whispered, his hand tightening on his sword, a cold, new hatred burning in his gut.